Kobelco SK135SRLC-2 Fault Code I113: Complete Diagnostic Guide

What is Kobelco SK135SRLC-2 Fault Code I113?

Fault Code I113 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal temperature reading detected by the Electronic Control Module (ECM). This code specifically signals that the ECM has identified either an open circuit, short circuit, or out-of-range voltage signal from the coolant temperature sensor.

The coolant temperature sensor plays a critical role in engine management for the Kobelco SK135SRLC-2's diesel engine. It provides real-time data that the ECM uses to adjust fuel injection timing, idle speed, and fan engagement. When this sensor fails or its circuit is compromised, the engine cannot optimize performance, potentially leading to poor fuel economy, hard starting in cold conditions, or engine overheating without warning.

Common Symptoms

When Code I113 is active on your SK135SRLC-2, operators typically experience:

• Warning light illuminated on the instrument panel (check engine or malfunction indicator)
• Engine running in default mode with fixed cooling fan operation at high speed
• Hard starting when the engine is cold, or rough idle during warm-up
• Excessive black smoke from exhaust due to improper fuel mixture compensation
• Inaccurate temperature gauge readings showing extremely high or low values regardless of actual engine temperature

Potential Causes

The most common technical causes for Code I113 in used SK135SRLC-2 excavators include:

• Faulty coolant temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged wiring harness near the sensor connector, especially where the harness routes along the engine block and experiences heat cycling
• Corroded or loose connector terminals at the sensor plug caused by coolant leaks or moisture intrusion
• ECM ground circuit failure affecting multiple sensor readings simultaneously
• Coolant contamination causing sensor element coating and false readings
• Broken or chafed wiring at known rub points near the engine mount brackets

How to Troubleshoot and Fix Code I113

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the wiring harness for obvious damage, melting, chafing, or oil contamination. Check the connector for corrosion, bent pins, or moisture. On used excavators, pay special attention to wear points where harnesses contact engine components or frame members.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At room temperature (20°C/68°F), resistance should typically read 2,000-3,000 ohms (consult service manual for exact specifications). Test the harness continuity from the sensor connector back to the ECM pins—resistance should be less than 5 ohms. Check for short to ground by measuring resistance between each circuit wire and machine ground (should read infinite/OL).

Step 3: Voltage Supply Check With the key on and sensor disconnected, measure reference voltage at the harness connector. You should see approximately 5 volts on the signal wire. If voltage is absent, trace the circuit back toward the ECM for breaks or check ECM fuses and power supply.

Step 4: Component Replacement If the sensor tests out-of-specification or the harness shows damage, replace the faulty component. For used machines, always replace connector seals and apply dielectric grease to prevent future corrosion. After replacement, clear codes using Kobelco diagnostic software or a compatible scan tool, then run the engine through a complete heat cycle to verify the repair.

Disclaimer: This guide provides general diagnostic information. Always consult the official Kobelco service manual for your specific machine serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Kobelco technician to prevent further damage to the ECM or engine systems.